Copper base alloy for metal evaporation



F. R.H ENsE| Erm. 2,447,979

COPPER BASE ALLOY FOR METAL EYAPORATION Aug. 24, 1948.

Filed July e. 1944 .T0 Mrz/UM PUMP P/mq/v/ 60,465

Hrm/P NEY Patented Aug. 24, 1948 COPPER BASE ALLOY FOR METAL EVAPORATIONFranz R. Hensel and Earl I. Larsen, Indianapolis, Ind., assignors to P.R. Mallory & Co., Inc., Indianapolis, Ind., a corporation of DelawareApplication July 6, 1944, Serial No. 543,634

2V Claims. (Cl. 75-153) This invention relates to improvements in metalevaporation.

An object of the invention is to improve the evaporation of copper andits alloys.

Other objects of the invention will be apparent from the description andclaims.

Figure 1 is a sectional elevation of a metal evaporation apparatus;

Figure 2 is a fragmentary cross-section of the tungsten filament coatedwith the metal to be evaporated; and

Figure 3 shows a wire loop of the metal.

The vaporization process for depositing silver, copper and other metalshas been known for some time and used commercially to some extent. Theprocessing as applied to silver is described in considerable detail inthe book Silver in Industry edited by Lawrence Addicks (Reinhold 1940),pages 291 to 296.

In carrying out the process the metal to be evaporated is usually hungon a tungsten filament as small loops of wire. Electric current is thenpassed through the lament to heat it and the wire loops are melted andthe fused metal clings to the filament and evaporates as the heating iscontinued. One diiiiculty which has been encountered with silver andcopper has been the failure of these metals to wet the tungstensufciently to cling to it during the vaporization process. The metaltends to ball up and drop olf the filament before it can be evaporated.It also sometimes tends to spatter during evaporation, probably due tothe accumulation of the liquid metal in large globules.

We have now discovered that this difficulty can be overcome in the caseof copper and satisfactory wetting of the tungsten filament obtained byadding a small percentage of lithium to copper or its alloys. Forexample, an alloy of Per cent Lithium .05

Platinum 5.00 Copper Balance 2 or iron may be present in percentagesranging from .001 to .5%.

Referring to the drawing, Figure 1 shows a metal vaporization apparatuscomprising a bell jar I0 resting on a pump plate II with a rubber gasketI 2 between them to afford a gas seal. The bell jar is connected to avacuum pump through pipe I3 and a Pirani gauge I4 may be provided tomeasure the degree of vacuum obtained.

The articles to be coated with a thin film of copper such as glassplates or mirror blanks I5 are mounted on the inside wall of acylindrical container I6 supported within the bell jar. The tungstenfilament I'I is mounted axially within the container and connected toinsulated terminals I8 and I9.

The copper alloy to be evaporated is hung on the spiral tungstenfilament as little wire loops 23 (Fig. 3) so that when the filamentheats up the loops will melt and cling to the filament.

Figure 2 is a fragmentary cross-section of the tungsten filament IIcoated with the fused alloy 2 I of copper preparatory to evaporation.

While speciflc embodiments of the invention have been described, it isintended to cover the invention broadly within the spirit and scope ofthe appended claims.

What is claimed is:

1. An alloy loop for metal evaporation formed of an alloy composed of.001 to 1% lithium, .25 to 20% of a metal selected from the groupconsisting of platinum and palladium and the balance copper.

2. An alloy wire for metal evaporation composed of about .05% lithium,5% platinum and the balance copper.

FRANZ R. HENSEL. EARL I. LARSEN.

REFERENCES CITED The following references are of record in the ille ofthis patent:

UNITED STATES PATENTS Number Name Date 1,291,106 Payne Jan. 14, 19191,923,955 Smith Aug. 22, 1933 2,178,233 Klatzow Oct. 31, 1939 2,196,302Hensel et al. Apr. 9, 1940 2,213,312 Hensel Sept. 3, 1940 2,330,062Lempert Sept. 21, 1943 2,413,604 Colbert et al Dec. 31, 1946 2,413,606Colbert et al Dec. 31, 1946

